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Tolerance to astigmatism in small aperture intraocular lenses

Poster Details

First Author: J.Tabernero SPAIN

Co Author(s): J. Marin P. Artal

Abstract Details

Purpose:

Small aperture corneal inlays are successfully used to extend depth of focus in presbyopic patients. The same concept could be also implemented in an intraocular lens with proper changes in the aperture size. The visual outcomes in pseudophakic patients will be affected by residual refractive errors. We evaluated theoretically the impact of uncorrected astigmatism in eyes implanted with an embedded mask.

Ray-tracing techniques were applied to the personalized biometric data from the eyes of 20 subjects (mean age 59 years, standard deviation 7 years). Corneal topography, ocular axial distances, angles and wavefront aberrations were available for each subject. An opaque mask with inner diameter of 1.36 mm was placed at IOL plane. The pupil of the eye was set to 3 mm of diameter. Astigmatism was induced in steps of 0.25 D (axis 90º) by placing a cylindrical lens at 15 mm from the corneal axis and then the eye's modulation transfer function was obtained for every eye from 0 D up to 3 D of induced astigmatism. The spatial frequency that corresponded to a modulation value of 0.2 (along the orthogonal direction to the axis of the astigmatism) was used as an image quality metrics and calculated in every eye with and without the small aperture.

Results:

In average, 1 D of uncorrected astigmatism for a pupil diameter of 3 mm would have the same optical impact than 1.9 D with the small aperture IOL implanted. This is an increasing of 0.9 D of tolerance to astigmatism. However, it should be noted that the mask with the lens is an annulus with an outer diameter of 3.23 mm. This implies that patients with natural pupil diameters significantly larger than 3 mm would exhibit a lower tolerance.

Conclusions:

The retinal image quality in eyes implanted with a small aperture mask embedded in an IOL to extend depth of focus is affected by the uncorrected astigmatism. Although there is an individual variability due to the particular eye's optics, the presence of the small aperture approximately doubles the tolerance to astigmatism. FINANCIAL INTEREST: One of more of the authors... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented